This invention relates to the field of work platforms. More particularly, the invention is directed toward an apparatus for assembly, repair and logistic transportation of, on and about a large truss structure. The immediate contemplated use and the impetus behind development is the construction of the National Aeronautics and Space Administration planned space station.
Preliminary studies conducted by the Natinal Aeronautics and Space Administration (NASA), on space station construction have identified the need for a mobile remote manipulator vehicle system. Such a logistics or utility device is envisioned to be outfitted with a spacecrane capability such as that utilized currently in the space shuttle cargo bay. At this stage of development it is thought that the presently employed shuttle remote manipulator system could be outfitted with a quick-disconnect from the shuttle fuselage and then used as the space crane on the mobile remote manipulator vehicle system. It is also probable that the mobile remote manipulator vehicle system will have two astronaut foot restraint positioning arms.
This mobile remote manipulator vehicle system is required during initial space station construction activities to position astronauts for manned extravehicular activity (EVA) assembly of the truss structure. It is also requisite to transport modules and pay loads from the shuttle cargo bay and position them for attachment to the truss structure. Subsequent to the initial space station construction activities, a mobile remote manipulator vehicle system is considered necessary for maintenance or repair activities and to provide a construction capability for future station growth or large space craft assembly and servicing. While the embodiment of the mobile remote manipulator vehicle system chosen for illustration is one designed for on-orbit zero gravity trusses, the invention is equally adaptable for one-gravity terrestrial applications where large truss structures might be employed.
The square bay truss structure of the planned space station suggest the need for a mobile remote manipulator vehicle system which can move in two orthogonal directions. This capability permits movement both along the space station keel structures between the modules and the solar array support structure as well as perpendicular along the solar array support booms. It is also desirable to optimize work area flexibility by providing a logistics platform capable of 360 degree rotation so as to maximize ability to work around the inexorably increasing attachments on a space station. An additional mobility requirement is a reversible drive which in effect expands the ability to move in two orthogonal directions to four and abrogates the possibility of trapping the mobile remote manipulator vehicle system in a corner.
Theoretically, a mobile remote manipulator vehicle system could be mounted on rails affixed to the space station truss structure. This would allow transition in a single orthogonal direction and involve complete detachment and reattachment to move in a perpendicular direction. Mounting rails onto the space station truss structure introduces additonal mass and significant design complexity which also must be considered. Positioning rails on the mobile remote manipulator system (instead of the truss) which "ride" on the truss hard points is possible. However, endless tracks (chains or belts) which provide mobility in this case must completely span two truss bays to ensure stability of the mobile remote manipulator system during motion. Such an arrangment avoids the mass and complexity of rails attached to the space truss structure but movement in a perpendicular direction is not enhanced. Also the undesirable feature of a system that must be two bays in length is introduced.
With the space shuttle program the only means of transporting the logistics to the on-orbit environment, packaging parameters must conform to the dimensions of the shuttle cargo bay. This is true for the logistics required to construct the space station as well as the mobile remote manipulator vehicle system. This limitation indicates a mobile remote manipulator vehicle that is no longer than one space truss bay in length. Limiting the dimensions to one truss bay will enhance usefulness for maintenance and construction activities, particularly in close proximity to the modular habitat or surface attached equipment.
A final design requirement for a viable mobile remote manipulator vehicle system is a drive system that utilizes electrical energy so as to be compatible with space station solar power. The system should employ rechargeable batteries and avoid umbilical cords. Control of all features of the mobile remote manipulator vehicle system should reside with the Extravehicular Activity Astronaut(s) to avoid hardline or remote system control links to a control station.